I have a Gateway desktop that occasionally loses the system sound. (The icon for the volume control in the task bar is X'd out with a warning that says no sound devices found.) The only way to get it back is to open Device Manager, then find the System section where it lists all the motherboard components. Uninstall the HD sound controller. Windows will "find" the HD sound controller and reinstall the driver for it on the next boot. I have been doing this at least once a month for 5 years. It always gets the sound working again. I have found no other solution to the problem.

So, let me ask, since you have AMD HD Audio, why do think you should have Realtek too? What make and model is your computer?

Hi rui,
It is very common for AMD FM series motherboards that have an on-board
HDMI connector to have both Realtek and AMD HD Audio.
I had one self-built desktop system with an MSI motherboard (since given to my brother)
and my current out-of-the-box Acer desktop that have both.

The Realtek is the standard audio jacks for speaker outputs, mic, and line-in.
The AMD HD Audio is usually only for the HDMI output connector.

wolferub,
It would be more helpful if you could give us the specific HP model number.
You could also run Belarc Advisor to show what motherboard it uses.